clarifications in the application of voltage for the bulk configuration

[Val]

i doing project in  Graphene on h-BN bilayer system.i need to apply voltage to the Graphene on h-BN bilayer system and i have to calculate Energy

gap.in the case of two probe system we can able to apply voltage using Source,Drain,gate.

But i am using Bulk configuration only.is it possible to apply voltage to the bulk configuration.if possible could you tell me the procedure.

[Anders Blom]

I'm assuming you want to apply a voltage perpendicular to the layers, otherwise you would just use a two-probe geometry? To introduce such a perpendicular voltage, or rather electric field, place two metallic regions on either side and assign different voltages to them. Be careful, however, not to use too high voltages, since the distances are very small (the field becomes very large).

This is similar to the approach in the benzene SET tutorial, except instead of the molecular levels you will now compute the band structure.

[Val]

thanks for your reply.i need to apply voltage perpendicular to layer.with this mail i attached my input file.if i apply voltage(+ or _ voltage) the bands are not shifting.could you tell me what mistake i did in my input file.

[Anders Blom]

I haven't had opportunity to try myself just yet, but one crucial aspect of using an electric field is that periodic boundary conditions no longer apply in the perpendicular direction. So, make sure to adjust to Neumann boundary conditions. Also, you don't need the extra space in the unit cell above and below the metal, the metal will screen all fields completely, so this vacuum space will just waste memory and time.